How to remove the Child in ActionScript3?

programming flash
1

I added the child each and Every time,once the child is added,when i add the next child the previous child is deleted this is my goal. am trying to remove the Child ,But Nothing Displayed in my screen. here my coding

[FONT=Consolas][COLOR=#00008B]var[/COLOR][COLOR=#000000] tf[/COLOR][COLOR=#000000]:[/COLOR][COLOR=#2B91AF]TextField[/COLOR][COLOR=#000000]=[/COLOR][COLOR=#00008B]new[/COLOR][COLOR=#2B91AF]TextField[/COLOR][COLOR=#000000]();[/COLOR][/FONT]
[COLOR=#000000]tf[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]text [/COLOR][COLOR=#000000]=[/COLOR][COLOR=#000000] chatData[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]message[/COLOR][COLOR=#000000];<---------[/COLOR][COLOR=#000000]here i add the text dynamically
listChat[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]addChild[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]tf[/COLOR][COLOR=#000000]);[/COLOR][COLOR=gray]// <----------------------------------here i added the child[/COLOR][COLOR=#000000]

[/COLOR][COLOR=#00008B]var[/COLOR][COLOR=#000000] t[/COLOR][COLOR=#000000]:[/COLOR][COLOR=#2B91AF]Timer[/COLOR][COLOR=#000000]=[/COLOR][COLOR=#00008B]new[/COLOR][COLOR=#2B91AF]Timer[/COLOR][COLOR=#000000]([/COLOR][COLOR=#800000]150[/COLOR][COLOR=#000000]);[/COLOR][COLOR=#000000]
t[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]addEventListener[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]
[/COLOR][COLOR=#2B91AF]TimerEvent[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]TIMER[/COLOR][COLOR=#000000],[/COLOR][COLOR=#000000]
[/COLOR][COLOR=#00008B]function[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]ev[/COLOR][COLOR=#000000]:[/COLOR][COLOR=#2B91AF]TimerEvent[/COLOR][COLOR=#000000]):[/COLOR][COLOR=#00008B]void[/COLOR][COLOR=#000000]
[/COLOR][COLOR=#000000]{[/COLOR][COLOR=#000000]
    tf[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]text [/COLOR][COLOR=#000000]=[/COLOR][COLOR=#000000] tf[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]text[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]substr[/COLOR][COLOR=#000000]([/COLOR][COLOR=#800000]1[/COLOR][COLOR=#000000])[/COLOR][COLOR=#000000]+[/COLOR][COLOR=#000000] tf[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]text[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]charAt[/COLOR][COLOR=#000000]([/COLOR][COLOR=#800000]0[/COLOR][COLOR=#000000]);[/COLOR][COLOR=#000000]

[/COLOR][COLOR=#000000]}[/COLOR][COLOR=#000000]

[/COLOR][COLOR=#000000]);[/COLOR][COLOR=#000000]

t[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]start[/COLOR][COLOR=#000000]();[/COLOR][COLOR=#000000]
listChat[/COLOR][COLOR=#000000].[/COLOR][COLOR=#000000]removeChild[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000000]tf[/COLOR][COLOR=#000000]);[/COLOR][COLOR=gray]// <----------------------------------here i remove the child[/COLOR][COLOR=#000000]

[/COLOR][FONT=Consolas][COLOR=#000000]}[/COLOR][/FONT]

how can i remove the child? help me,Thanks in Advance!